1. Field of the Invention
This invention relates generally to drilling equipment used particularly in the hydrocarbon production industry and specifically to an elevator system and method for running or raising tubulars in a well.
2. Description of the Prior Art
In the hydrocarbon production industry, tubular goods, including drill strings, casings and tubing and often referred to simply as tubulars, must at varying stages be run, i.e. lowered, into or raised from a well. Elevators are devices which support the tubular for the purpose of raising or lowering it. An elevator may clamp along the side of a tubular using slips and dies to exert a radial clamping force on the tubular wall, or an elevator may use a bushing to support the tubular at the lower lip of a box connector. The latter method is preferable for deep water production or when running heavy casings or landing strings, because a slip can exert damaging crushing forces on the tubular under high hook loads.
FIGS. 1 and 2 show one typical elevator setup of prior art where an elevator (10) is suspended from a top drive mechanism (9) by a pair of bails, or links (14), which have eyes (16, 18) at both ends. The top drive mechanism (9) is in turn suspended by a traveling block (12) and wire rope (19) rigged from a crown block (not shown) located in the top of the drilling rig. The upper eyes (16) of the pair of bails (14) are hooked to the link supports (20) of the top drive (9), and the lower eyes (18) of the pair of bails (14) are hooked to the ears (22) protruding from the elevator (10). The bails (14) are secured to the elevator ears (22) by locking mechanisms (25) to prevent the bails (14) from inadvertently becoming uncoupled from the elevator (10). The elevator (10) and the supported tubular (24) are thus raised and lowered by the traveling block (12)/top drive (9) and bails (14). All the components in this series are designed to carry the expected loads.
The top drive (9) is used in place of a conventional rotary table and Kelly bushing to rotate the tubular during rotary drilling. Using hydraulic or electric motors (11) and a gear train (13) suspended above the drill string (24) enables the drill string to be rotated continuously while being lowered into or raised from a well. The top drive mechanism slides up and down along frame members (15) to check rotation of the top drive in reaction to the spinning of the tubular (24) while allowing free vertical movement of the device.
A spider, much like an elevator, is a device which supports a tubular to prevent it from descending into a well when it is not held by an elevator. Unlike an elevator, however, the spider is designed to remain on the drilling deck and is not moved vertically. When the elevator, suspended by the traveling block, nears its high limit of travel (when raising a tubular) or its low limit or travel (when running a tubular), or when a stand is required to be added or removed, the elevator must be repositioned in order to continue the operation. The spider supports the tubular prior to the elevator releasing the tubular. Thus, the tubular is held in place while the elevator is repositioned. Once the elevator carries the tubular at a new location, the spider is disengaged allowing the tubular to freely pass through the spider or for the spider to be moved completely clear of the tubular.
In some drilling platforms, particularly those used for deep water production, a large number of stands is required to be on hand. In such platforms, the derrick may become cluttered, hindering operations and increasing operation time. To simplify the operation, it has been known to use a first elevator as a temporary substitute for a spider to support a tubular and a second elevator, coupled to the traveling block, to lower the tubular string. Each elevator is preferably equipped with a door for side entry of a tubular. When the second traveling elevator is holding the tubular, the first spider elevator is moved clear of the tubular. The second elevator and tubular are lowered. When the second elevator has been lowered to the rig floor, the bails are removed from the second elevator and attached to the nearby first elevator. The second elevator now acts as the spider, holding the tubular while the first elevator is repositioned towards the top of the string where it supports the tubular or is used to move a new stand to the top of the string which is coupled thereto. The second elevator then releases the tubular and is moved clear of the tubular, and the first elevator lowers the tubular into the well. When the first elevator reaches the rig floor, the elevators are again swapped in a process sometimes referred to as circulating the elevators. The same process is used in a reverse sequence for raising a tubular. Because both elevators change their location continuously during this process, there is no need for elevator/spider differentiation.
A coordinated dual elevator system simplifies the process of circulating the elevators. A dual elevator system may incorporate features such as a shuttle table to receive the traveling elevator on deck for use as a spider, to readily move a spider elevator off of well center to prepare its use as a traveling elevator, and to vacate the landing table for receiving the next traveling elevator. In other words, the shuttle table is used to move the spider elevator into and out of engagement with a tubular at well center.
Many elevators and spiders used today employ power operated internal mechanisms, e.g., power doors and/or power slips. The powered elevators and spiders are commonly hydraulic, but can be pneumatic or electric. When circulating the elevators, power and control lines can interfere with deck operations, becoming entangled or snagging on objects. Additionally, uncoupling and re-coupling supply lines is also a burdensome manual process, particularly for hydraulic systems. Therefore, the process of circulating elevators has traditionally been limited to manually operated elevators. A method and apparatus which simplifies the supply of power to powered elevators when circulating the elevators is desirable.
3. Identification of Features of one or more Embodiments of the Invention
A primary object of the invention is to provide a method and apparatus for increasing the efficiency of drilling operations by automating the process of circulating elevators and by allowing for the use of powered elevators in the process of circulating elevators.
Another object of the invention is to provide a method and apparatus which prevents the need for riggers or other personnel to manually connect or disconnect power and control lines for an elevator or to manually move an elevator from well center to an offset standby position or vice versa.
Another object of the invention is to provide a method and apparatus for providing power and control to an elevator in a manner which does not cause power or control lines to hamper or otherwise interfere with deck operations.
Another object of the invention is to promote operator safety by providing for total hands-free operation of the elevator.